Department of Cell Biology and Neuroscience, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
J Histochem Cytochem. 2010 May;58(5):443-53. doi: 10.1369/jhc.2010.955690. Epub 2010 Feb 1.
Old and unneeded intracellular macromolecules are delivered through autophagy to lysosomes that degrade macromolecules into bioactive monomers such as amino acids. Autophagy is conserved in eukaryotes and is essential for the maintenance of cellular metabolism. Currently, more than 30 autophagy-related genes (Atgs) have been identified in yeast. Of these genes, the18 that are essential for autophagosome formation are also conserved in mammalian cells. Atg9 is the only transmembrane Atg protein required for autophagosome formation. Although the subcellular localization of the Atg9A protein (Atg9Ap) has been examined, little is known about its precise cell and tissue distribution. To determine this, we produced an antibody specific to mouse Atg9Ap. The antibody recognized both non-glycosylated and glycosylated Atg9Ap, which have molecular masses of approximately 94 kDa and 105 kDa, respectively. Although Atg9Ap was ubiquitously detected, it was highly expressed in neurons of the central nervous system. In Purkinje cells, Atg9Ap immunoreactivity was localized in the endoplasmic reticulum (ER), trans-Golgi network (TGN), lysosomes/late endosomes, and in axon terminals. These results suggest that Atg9Ap may be involved in autophagosome formation in the ER and axon terminals of neurons, the TGN, and lysosomes/late endosomes.
衰老和不再需要的细胞内大分子通过自噬作用被递送到溶酶体中，溶酶体将大分子降解为生物活性单体，如氨基酸。自噬在真核生物中被保守，对于维持细胞代谢是必不可少的。目前，已经在酵母中鉴定出超过 30 个与自噬相关的基因（Atgs）。在这些基因中，对于自噬体形成必不可少的 18 个基因也在哺乳动物细胞中被保守。Atg9 是形成自噬体所必需的唯一跨膜 Atg 蛋白。尽管已经研究了 Atg9A 蛋白（Atg9Ap）的亚细胞定位，但对其确切的细胞和组织分布知之甚少。为了确定这一点，我们产生了一种针对小鼠 Atg9Ap 的特异性抗体。该抗体识别未经糖基化和糖基化的 Atg9Ap，它们的分子量分别约为 94 kDa 和 105 kDa。尽管 Atg9Ap 广泛存在，但它在中枢神经系统的神经元中高度表达。在浦肯野细胞中，Atg9Ap 免疫反应性定位于内质网（ER）、高尔基网络（TGN）、溶酶体/晚期内体和轴突末端。这些结果表明，Atg9Ap 可能参与神经元的 ER 和轴突末端、TGN 和溶酶体/晚期内体中的自噬体形成。
